N-aryl-n&#39;-(p-hydroxyphenyl) ureas as antioxidants for petroleum hydrocarbon fuels



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' NdnynNwpnvonoxrurrntsvi-nunms AS AN- ..CTIOXIDANTS FOR PETROLEUM HYDROCAR- BON FUELS l l 0, Depree, Royal g grror sito Ethyl Corporation, New York,

N; Y., a coiporation of Delaware No Drawing xii-nannies 16, 1954,

1 7 Serial No. 423,835

4 Claims. (Cl. 44- 71) 1 application is a cbntiniiatioh-in-pait .of our icopending application serial Numberfi2 68,455, filed Januthe field, of oxidation inhibition. W eyhave discovered,

however, an by substituting the free amine of N-p-hydroxyphenyl urea with a phenyl group, and further substitute either this phenyl or the hydroxy phenylated nitrogen with a hydrocarbon radical we obtain a class of substances which are powerful gasoline antioxidants. So far as we are aware it has not previously been known that the mere addition of such hydrocarbon groups to an otherwise inactive compound would produce thereby materials which would prevent deterioration of petroleum hydrocarbons by the action of oxygen.

I herefore it an object of this invention to provide a new class of antioxidant materials useful in protecting petroleum hydrocarbons from deterioration in the presence of oxygen or air. In particular it is an object of this invention to provide liquid petroleum hydrocarbon duels of the gasoline type stable to oxidation.

In accordance with our invention we provide fuel compositions containing ureas of the structure iTypical hydrocarbon groups which we employ include methyl, ethyl, propyl, n-butyl, sec.-b-utyl, isobu-tyl, octyl, dodecyl, pentadecyl, cyclobutyl, cyclohexyl, benzyl, phenethyl, phenyl, o-tolyl, m-tolyl, p-tolyl, the xylyls, ophenylene, allyl, propenyl, butenyl, crotyl, methallyl, phytyl, isobutenyl, oleyl, cyclohexenyl, and the like.

The free amine from which these antioxidants can be considered as being derived, in addition to being inactive as an antioxidant, possesses a low degree of solubility in petroleum hydrocarbons. However, in accordance with this invention, we not only increase the solubility in petroleum hydrocarbons but obtain the unexpected result that thereby is created an antioxidant material which is as potent as many commercial antioxidants and more potent than several.

In general the compounds of these compositions are prepared readily and in good yield by combining arylisocyanates with p-aminophenols. In the examples which follow are illustrated the preparation of specific examples of the antioxidants of this invention and in these examples all parts and percentages are by weight.

EXAMPLE I N-(p-tolyl)-N'-(p-hydr0xyphenyl) urea.--To a vessel provided with an agitator, means for returning reflux to the reaction vessel, means for introducing liquid reactants,

Sees- Pwt 2,785,965 res terss and for silpplying heat was-addedlflfl parts-t p- I aminophenol and 300 parts of toluene. This mixture was heated to a temperature of 50 C. and 1 20 parts of ptolylisocyanate was added over a period of one and onequarter hours. 'At the end of theaddition the mixture was urea was recovered in '97 per cent, yield based upon the pan-iinophenol employed. This product melted at a temperature of 214 to 216 C.

When we treat o-tolyl isocyanate and 3-(-rn'ixed)a myl- I phenylisocyanate with 'p aminophenol according to the process described in Example I, we obtain N-ortolyl-Nfdphydroxyphenyl) urea, and N (m-(mixed) amylphenyl -N'- .(p-hydroxyphenyU-urea, respectively.

ordarice'withthe procedure of Example I, N-methyl-p- 'riophenol iiibenzene treated withphenylisocyahate. The product was recovered as a white crystalline o id,

"il r niu eNominate: ni a e N- s p aminophenol and N cyc1ohexyl p .aminophenol a: e treated with phenylisocyanate in accordance with the preceding example, N-phenyl-N-propenyl-, N,N'-diphenyl-, and N phenyl-N-cycl ohexyl-N-( p hydroxyphenyhurea are obtained respectively.

EXAMPLE III N-phenyl-N-n-butyl-N'- p-hydroxyplzenyl)urea.--In a process similar to Example I, parts of phenylisocyanate was treated with 137 parts of N-butyl-p-aminophenol to produce N phenyl-N-n-butyl-N'-(p-hydroxyphenyl)- urea having a melting point of 158 C.

To illustrate specific examples of that embodiment of this invention wherein two hydrocarbon groups are substituted in the general formula of the antioxidant, when we treat, as described in Example I, o-tolylisocyanate with N-methyl-p-aminophenol, and p-diphenylisocyanate with N-methyl-p-aminophenol we obtain N(o-tolyl)-N- methyl-N-(p-hydroxyphenyDurea, and N-(p-diphenyl)- '-methyl-N'-4-hyd.roxyphenyl urea.

The compounds of this invention are excellent antioxidants and we have illustrated this property in Table I, wherein are listed the results obtained by determining the oxidation stability of gasoline according to the Induction Period Method, ASTM designation: D525-46, .as fully described in Part III-A, ASTM Standards for 1946. We have employed gasoline in this determination since it is representative of an important class of industrial products which are susceptible to deterioration, and -for which it is important to provide stabilizing materials. The column headed IPI lists the Induction Period Increase, in minutes, over that of the gasoline in the absence of the antioxidants of this invention. That is, under the conditions of test, each gasoline exhibits a period, typical of the gasoline, wherein oxygen is not absorbed. In the presence of the inhibitors this period is increased by the amount listed under IPI. The lack of eifectiveness of N- (p-hydroxyphenyl)urea is shown by compound No. 4 in the table.

Table I EFFECT ON INDUCTION PERIOD INCREASE 0F GASOLINE No. Additive IPI, Min.

N-Phenyl-N-methyl-N-(phydroxyphenyl) urea 225 N- (D-tolyl) -N-(p-hydroxy'phenyl) urea 170 N-PhenyI-N-n-butyl-N-(p-hydroxypheny rea. N -(p-hydroxyphenyl) urea 25 To illustrate the improved solubility characteristics of the N-aryl-N'-hydroxyphenyl ureas of this invention, we have listed in Table II the solubility, expressed as milligrams of compound per 100 millimeters of solvent, of representative members of these compounds in isooctane, representative of a petroleum product, and have contrasted therein "the solubility of the N-phenyl-N-p-hydroxyphenyl urea unsubstituted with hydrocarbon groups. It is evident that we can obtain more than :a four-and-one-half-fold increase in the solubility of the N-aryl-N'-hy-droxyphenyl urea by merely substituting one methyl group thereon.

In general, the stabilized fuel compositions of this invention contain an antioxidizing amount of the antioxidant, that is an amount of antioxidant ingredient sufficient to inhibit deterioration. In general, we prefer to employ about 0.01 weight percent of the antioxidant, although depending upon the nature of the gasoline being inhibited this quantity may be varied from this limit.

We have disclosed a number of embodiments of this invention and illustrated several methods whereby these materials can be prepared. However, this invention is not intended to be limited to the specific examples herein.

!We claim:

:1. A fuel composition stable to oxidation consisting essentially of a liquid petroleum hydrocarbon fuel of the gasoline type normally susceptible to deterioration in the presence of oxygen and in quantity SllffiClBHt to inhibit such deterioration, an N-phenyl-N (p-hydroxyphenyl)- urea antioxidant ingredient selected from the group consisting of N-phenyl-(N-methyl-N'-p-hydroxyphenyl)urea, N (p-tolyl)-N'- (p-hydroxyphenyDurea, and N-pheny1-N'- n-buty1-N'(p-hydroxyphenyl)urea.

2. The composition of claim 1 wherein said N-phenyl- N'-(p-hydnoxyphenyl)urea is N-phenyl-(N methyl-N phydnoxyphenyD-mea.

3. The composition of claim 1 wherein said N-phenyl- N (p-hydroxyphenyl)urea is N-phenyl-N'-n-butyl-N'-(phydroxyphenyDurea.

4. The composition of claim 1 wherein said N-phenyl- N'-(p-hydroxypheny1)urea is N-(p-tolyl)-N'-(p-hydroxyphenyl)urea.

References Cited in the file of this patent UNITED STATES PATENTS 2,683,081 Hill et al July 6, 1954 

1. A FUEL COMPOSITION STABLE TO OXIDATION CONSISTING ESSENTIALLY OF A LIQUID PETROLEUM HYDROCARBON FUEL OF THE GASOLINE TYPE NORMALLY SUSCEPTIBLE TO DETERIORATION IN THE PRESENCE OF OXYGEN AND IN QUANTITY SUFFICIENT TO INHIBIT SUCH DETERIORATION, AN N-PHENYL-N''(P-HYDROXYPHENYL) UREA ANTIOXIDANT INGREDIENT SELECTED FROM THE GROU CONSISTING OF N-PHENYL-(N''-METHYL-N''-P-HYDROPHENYL)UREA, N-(P-TOLY)-N''-(P-HYDROXYPHENYL)UREA, AND N-PHENYL-N''N-BUTYL-N''-(P-HYDROXYPHENYL)UREA. 